Large Berry phases in layered graphene

Understand

Brillouin zones of graphene systems possess Dirac points, where band degeneracies occur.

• We study the variety of (and large magnitude) phases that the electronic states can acquire when a uniform time-dependent electric field carries the electrons around one or more Dirac points in a non-concentric fashion.
• An experimentally accessible determination of excess Berry phases is proposed involving the Zitterbewegung of electronic current near an orthogonality point in adiabatic motion.